(a) Schematic of the microfluidic device with a built-in horseshoe structure. Bacterial suspension is injected from the inlets and collects in a pair of vortices induced by the oscillating microbubble trapped in the horseshoe. (b) The microbubble trapped in a horseshoe structure undergoes weakly linear oscillations. is the amplitude of oscillation of a bubble with diameter. A pair of vortices is generated upon applying the radio frequency signal. 1.9 μm polystyrene microbeads are used as flow tracers to demonstrate the flow field when the transducer is (c) off and (d) on. Structure of the horseshoe is shown with white lines for visualization.
Contours of FLI, which indicate bacterial concentration, are plotted for RP437 E. coli at different time snapshots. (e)-(h) Bacteria collect in the vortex pair as shown by FLI contours overlaid on the flow streamlines (solid blue lines).
FLI, indicating bacterial concentration, is plotted along the red-line across the vortex, as shown in the inset, for (a) low motile () and (b) high motile (RP437) E. coli versus time. Applied voltage is (enhanced online). [URL: http://dx.doi.org/10.1063/1.4771407.1] [URL: http://dx.doi.org/10.1063/1.4771407.2]10.1063/1.4771407.110.1063/1.4771407.2
(a) A biofilm streamer formed after three minutes of applying the voltage (OD600 = 0.25, ). Rapid E.coli biofilm formation in (b) a microfluidic channel after 30 min (OD600 = 2). Aggregate of E. coli formed the shape of two vortices in cavitation streaming of an oscillating bubble (). The bacteria remained aggregated even after the removal of the RF signal. (c) A microfluidic channel with oscillating bubbles () on the side walls (OD600 = 2) (enhanced online). [URL: http://dx.doi.org/10.1063/1.4771407.3] [URL: http://dx.doi.org/10.1063/1.4771407.4]10.1063/1.4771407.310.1063/1.4771407.4
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